In the image data input apparatus such as copying machine, image scanner, facsimile and so on, a solid state image forming device, such as so called CCD, is used. In this solid state image forming device 101, many photoelectric transforming device 102 having a dimension of some micro meters square, are arranged in line as shown in FIG. 8(a), and the image data input apparatus is arranged to achieve the image data input in that image of document 103 is focused by an image focusing lens 104 as shown in FIG. 9. Further, recently a solid state image forming device for colored image that has 3 peaks of spectroscopic sensitivity in R, G, B respectively to input colored image as shown in FIG. 8(b). This photoelectric transforming device is a device to transform optical energy to electrical energy, and in many times it is called as “pixel” when it is used for light receiving portion of the solid state image forming device such as CCD, hereinafter in this specification the photoelectric transforming device 102 is referred to as pixel 102.
In an image data input apparatus utilizing the solid state image forming device 101, the positional accuracy of line of pixels becomes very important because there is an importance that a line image from an image focusing lens 104 is focused on the pixels of the solid state image forming device 101 while the predetermined accuracy in the optical characteristics are fulfilled in order to realize better image input performance. To attain this, the position of the solid state image forming device 101 with regard to the image focusing lens 104 must be adjusted with a slight movement in five axes of x, y, z, β and γ respectively as shown in FIG. 9. Generally, it is requested that the positional accuracy of the solid state image forming device 101 of this kind is highly accurate in the five axes.
However, even the positioning adjustment has been attained with high accuracy, discrepancy may be happened when the solid state image forming device 101 is fixed, it causes an increase in costs because of need for more positioning adjustment again or disposal of scrap of the unit. Up to now the fixing is mainly achieved by screws, however, the amount of discrepancy is large such as ranged between some tens micro meters and some hundreds micro meters, sufficient precision of positioning could not be secured. For that reason, a fixing structure for solid state image forming device 101 to be attached without happening of discrepancy is long desired.
For example, in the Japanese Patent Laid Open No. Hei 5-328017 an arrangement in order to attain accurate positioning adjustment and fixing between CCD line sensor and image focusing lens utilizing a positional adjustment mechanism using wedge screw, ball and compressed spring, is disclosed. However, by this arrangement, because many complicated mechanism and parts are required and total number of parts is increased, it causes the increase of costs.
Accordingly, at present a fixing by adhesive material is mainly tried which is thought that amount of discrepancy is much less than that by screws and that the number of parts does not almost increase. When the fixing by adhesive material is classified roughly, one is a contacting adhering method in which the objects to be fixed together is contacting each other and adhered, and another is a caulking adhering method in which a space is made between the objects to be fixed together and the adhesive material is filled between the space to adhere, is not contacting with space.
As a technology utilizing this caulking adhering method, there is one which is disclosed, for example, in Japanese Patent Laid Open No. Hei 7-297993. According to the patent, an arrangement is disclosed in order to attach a holding member for solid state image forming device and a fixing member for solid state image forming device together with high accuracy on which an image focusing lens is fixed. That is to say, a projecting portion is arranged on the fixing member for solid state image forming device, and a hole portion with much larger diameter than the projecting portion is arranged on the holding member for solid state image forming device, then the above stated two members are placed each other in predetermined positional relation while the projecting portion is inserted into the hole portion, and they are fixed by the adhesive material which is filled the space at the inserted portion in a state with keeping their positional relation. In this arrangement the amount of space is settled so that the objects to be fixed are not contacting each other even when the shape and size of the objects to be fixed are different by scattering within the tolerance.
When ultraviolet setting type material is utilized as adhesive material, after it is painted on adhering surface of the object to be adhered 105, the object is adjusted the positional relation to the object to be adhered 107, then the adhesive material 106 is hardened to fix the object to be adhered 105 onto the object to be adhered 107 by irradiating ultraviolet to the ultraviolet setting adhesive material 106 through a light guide 108 from a space between the objects to be adhered 105 and 107 as shown in FIG. 10.
However, in the method disclosed in the Japanese Patent Laid Open No. Hei 7-297993, because the amount of space between the inserted portion is settled so that the projecting portion and the hole portion would not contact each other, and the adhesive material is filled the space to fix, it has problems listed below. Hereinafter the problems of this caulking adhering method are concretely explained with reference to FIG. 11.
In FIG. 11, the reference numerals 105′ and 107′ designate objects to be adhered, 106′ designates the adhesive material. The object to be adhered 105′ is fixed onto the object to be adhered 107′ by a manner that the adhesive material 106′ is filled in the space between the objects to be adhered 105′ and 107′, and hardened after the objects to be adhered have adjusted their positional relation on the predetermined position. The objects to be adhered 105′ and 107′ correspond to the outer surface of projecting portion and the inner surface of hole portion in the specification of Japanese Patent Laid Open No. Hei 7-297993. Herein, a predetermined space B must be prepared after the positional adjustment in order to keep space between 105′ and 107′ without contacting each other and to get required adhesive force by filling required amount of the adhesive material. When supposing an amount of dispersion in positional discrepancy of the adhering surface 105a of the object to be fixed 105′ which includes space for positional adjustment, is A, and an amount of dispersion in positional discrepancy of the adhering surface 107a of the object to be fixed 107′ which includes space for positional adjustment, is C, then film thickness of the adhesive material 106′ becomes a range from B at the minimum and to A+B+C at the maximum, and it becomes dispersing in a range A+C. Further, when the objects to be fixed 105′ and 107′ have the dispersion I and J from the surface accuracy at the adhering surfaces, the film thickness of adhesive material 106′ tends to have more dispersion in that amount.
Generally, as the adhesive material shrinks when it is hardened, it becomes required that the painting amount of adhesive material must be reduced as little as possible in order not for the objects to be fixed to have the positional discrepancy after the adhesive material is hardened. On the contrary, as the film thickness of adhesive material can not be made less than B in the above described caulking adhering method, it was impossible that the amount of positional discrepancy is made to remain within the tolerance after fixing.
In addition, the amount of shrinkage of the adhesive material after hardened, varies in accordance with the dispersion because the dispersion of film thickness of the adhesive material occurs up to A+C+I+J in total. In the result of this, when the position of objects to be fixed 105′ and 107′ after fixed, are dispersed more, there was a case in that the positional discrepancy became much larger.
Commonly, the volume shrinkage rate of ultraviolet setting adhesive material is in a level of range from 5 to 10 percent. When considering a case that the volume shrinkage rate is 6%, it shrinks about 2% in each respective three directions. Presuming the minimum space B is 0.5 mm, it shrinks in its direction about 10 μm by the shrinkage of adhesive material alter hardened. And presuming the total sum A+C+I+J of dispersion film thickness is also 0.5 mm, the shrinkage of about 10 μm occurs again by it, the positional discrepancy up to 20 μm at the maximum occurs.
To solve this kind of problems, there is a fixing structure disclosed in, for example, Japanese Patent Laid Open No. Hei 10-309801, that absorbing the positional discrepancy by a shrinkage of the adhesive material and increasing the positional accuracy of the fixed objects by means of an intermediate holding member lying between the objects to be fixed when they are fixed by the caulking adhering method.
This fixing structure is characterized in that an intermediate holding member is lying between the inkjet head and the head holding member, then the intermediate holding member is fixed onto an inkjet head by the adhesive material and at the same time it is fixed onto the head holding member through the adhesive material in order to attach an inkjet head onto a head holding member with high accuracy in a fixing structure for the inkjet head. According to this fixing structure, the positional discrepancy between the inkjet head and the head holding member can be made decreased when they are fixed because the shrinkage is absorbed by that the intermediate holding member moves so as to get closer to the inkjet head and to the head holding member in accordance with the shrinkage when the adhesive material is hardened and shrunk.
There has been proposed a fixing structure for solid state image forming device by which high accuracy of positioning can be attained with simple structure that an image focusing lens holding member and the solid state image forming device are fixed by means that the image focusing lens holding member and an intermediate holding member are adhered by the caulking adhering method and at the same time the intermediate holding member and the solid state image forming device are adhered by the caulking adhering method when the above stated fixing structure is applied to the fixing for solid state image forming device.
However, according to this fixing structure by adhesion, the high positional accuracy can be attained in low cost without necessity of complex mechanism, it is not easy to separate each parts again after fixing. To separate each parts, several method can be applicable that solvent is added to the adhered portion to melt the adhesive material, or a tool is inserted to separate the adhered portion mechanically, since, they are not good method to separate them because the former method takes so long time to melt and the latter method deforms or breaks the parts by the tool when the film thickness of the adhesive material is about some ten μm.
For example, there were cases that a digital copying machine is recalled from market because it has defect in the image focusing lens holding member itself and there are no defect in the solid state image forming device, the machine cannot help be scrapped with the solid state image forming device attached by the adhering method because there is no way to separate well the adhered portion. Not only for case that the products are recalled from market, but for case a fact has become clear after adhering that image focusing lens has defect, the machine also must be scrapped with the solid state image forming device.
It was a problem of cost increasing or yield of production decreasing and it is a problem from a view point of protection of environment which goes against the stream of the resource saving that parts without defect adhered to a parts with defect, is also scrapped with the defected parts. Especially, because the solid state image forming device and its circuit board attached to the solid state image forming device are expensive as the materials themselves, it was a serious problem to make them strapped though they don't have any defect.
The present invention has been made with regard to the above described problem, and it has an object to provide a fixing structure for solid state image forming device made inexpensively and easily by simple caulking adhering method with keeping high positional accuracy, by which it is achieved that the solid state image forming device can be separated easily from the image focusing lens holding member when the image focusing lens holding member has a defect, and only the image focusing lens holding member can be scrapped.